The Role of Plutonium in Nuclear Reactors

The neutrons absorbed by in a natural uranium reactor are not wasted, but lead eventually to the production of Pu, which is also fissile. The sequence for production of Pu is as given below  

The plutonium is formed as the result of two successive jS decays with the half-lives indicated t t239 

The production of from is known as conversion and is called a fertile material. Another fertile material of importance is thorium, where the Th is converted to fissile by the following sequence of events  

While the production of will take place automatically in any 

The buildup of Pu in a reactor fueled with natural or low-enrichment uranium is of value in extending the life of the fuel charge. As the content decreases due to bum-up, the corresponding buildup of Pu reaches the point where more than half of the fissions taking place in the reactor are occurring in the plutonium. The prediction of the effect of Pu buildup is complicated by the fact that irradiation of the Pu formed leads eventually to the formation of another fissile material, Pu through the following sequence  

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